I've setup repositories on both my linux PC & android mini pc and added jabber account on both. They are both at my home network. They detected each other fine. But when it comes to syncing files, there's a message which says "Unable to download files from your other devices" with a button for "add a cloud repository". I don't need to add a cloud repository since both computers are at the same network? Or am I missing something in the architecture of git-annex that even to sync two local computers in the same LAN, annex would still need an external repo? (and if so, why would that be?)
I'm not really willing to add an external repository as I intend to add large files and I don't want that they are first uploaded using a slow connection & then re-downloaded.
What am I missing?

To make computers on your network directly communicate, they must be connected together using the user interface. This is normally using the local pairing interface. But local pairing does not yet work on Android. The best you can do to instead on your Android device, add the Linux PC as a ssh server. This will let the Android device send/receive files directly with it over the local network.

It's been a while since the android app has worked. Are there any plans to get it working on modern Android versions? I assume it's pretty low demand, but it would make git-annex just so much more useful for me.

To clarify, I am experiencing this issue, as will everybody using Android >=6: